Methods for producing 1,5,7-triazabicyclo[4.4.0]dec-5-ene by reaction of a disubstituted carbodiimide and dipropylene triamine

ABSTRACT

Methods for producing 1,5,7-triazabicyclo[4.4.0]dec-5-ene using a disubstituted carbodiimide, dipropylene triamine and optionally an ethereal solvent and/or an alcohol are disclosed. Use of 1,5,7-triazabicyclo[4.4.0]dec-5-ene produced by this method in an electrodepositable coating composition, and electrophoretic deposition of such coating onto a substrate to form a coated substrate, are also disclosed.

FIELD OF THE INVENTION

The present invention relates to methods for producing1,5,7-triazabicyclo[4.4.0]dec-5-ene.

BACKGROUND OF THE INVENTION

It is known that bicyclic guanidines, such as1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD), are chemically active and canbe used to catalyze a variety of chemical reactions. An importantconsideration in the commercial exploitation of bicyclic guanidines as acatalyst (for any reaction) is that bicyclic guanidines be relativelyinexpensive to purchase and/or easy to produce.

Published methods for synthesizing bicyclic guanidines, however, areoften complicated, such as by using a multiple step and/or timeconsuming synthesis process. Others use prohibitively expensive and/orhazardous starting materials. Further, many published methods do notproduce high yields of the desired products, or produce byproducts, suchas aniline, that are difficult to separate from the bicyclic guanidinesand may themselves be hazardous. Also, many of these methods producebicyclic guanidines of different types that may be difficult to separatefrom one another, and/or produce bicyclic guanidines in forms that aredifficult to handle.

There is therefore a need for safe and efficient methods for producingbicyclic guanidines.

SUMMARY OF THE INVENTION

The present invention is directed to a method for producing1,5,7-triazabicyclo[4.4.0]dec-5-ene comprising forming a mixturecomprising a disubstituted carbodiimide, dipropylene triamine and anethereal solvent and/or an alcohol; and heating the mixture to cause thedisubstituted carbodiimide to react with the dipropylene triamine.

The present invention is further directed to methods for producing1,5,7-triazabicyclo[4.4.0]dec-5-ene comprising forming a mixturecomprising a disubstituted carbodiimide and dipropylene triamine; andheating the mixture to cause the disubstituted carbodiimide to reactwith the dipropylene triamine.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to methods for producing bicyclicguanidines. More specifically, the present invention is directed tomethods for producing 1,5,7-triazabicyclo[4.4.0]dec-5-ene comprisingreacting a disubstituted carbodiimide with dipropylene triamine(“DPTA”), also known as bis(3-aminopropyl)amine.

As used herein, the term “disubstituted carbodiimides” refers to acompound having the formula RN═C═NR¹, wherein R and R¹ independentlycomprise an alkyl group, an aryl group or mixtures thereof. R and R¹ canbe the same or different. In certain embodiments, the disubstitutedcarbodiimide comprises a dialkyl carbodiimide and the R/R¹ group is analiphatic and/or cycloaliphatic alkyl group, for example, having 1 to 10carbons; particularly suitable dialkylcarbodiimides include, withoutlimitation, N,N′-diisopropylcarbodiimide (DIC) (i.e. when R/R¹ is anisopropyl group), N,N′-dicyclohexylcarbodiimide (DCC) (i.e. when R/R¹ isa cyclohexyl group), N,N′-di-tert-butylcarbodiimide (wherein R/R¹ is atert-butyl group), and any combinations thereof.

In certain embodiments, the disubstituted carbodiimide comprises adiaryl carbodiimide and the R/R¹ group is an aryl group. A particularlysuitable diarylcarbodiimide is N,N′-di-p-tolylcarbodiimide (wherein R/R¹is a toluene residue). In certain embodiments, combinations of one ormore dialkylcarbodiimides and/or one or more diarylcarbodiimides areused.

In certain embodiments, the method for producing1,5,7-triazabicyclo[4.4.0]dec-5-ene includes first dissolving thedisubstituted carbodiimide in an ethereal solvent and/or in an alcoholprior to reacting the disubstituted carbodiimide with DPTA. Theseembodiments are sometimes referred to herein as the “solvent process”.In alternative embodiments discussed further below, methods forproducing 1,5,7-triazabicyclo[4.4.0]dec-5-ene do not utilize an etherealsolvent or alcohol, and are sometimes referred to herein as the“solventless process”.

In general, the solvent process begins by dissolving a disubstitutedcarbodiimide in an ethereal solvent and/or in an alcohol. Next,dipropylene triamine is added to the dissolved disubstitutedcarbodiimide. In some embodiments, the disubstituted carbodiimide andsolvent and/or alcohol mixture is heated, such as to a temperature of60° C., prior to the addition of the DPTA and in some embodiments themixture is heated to about 60° C. after addition of the DPTA. Themixture is then further heated to an elevated temperature and held for asufficient period of time to react the disubstituted carbodiimide anddipropylene triamine, first forming an intermediate, (generally anN,N′-disubstituted monocyclic guanidine), and then forming1,5,7-triazabicyclo[4.4.0]dec-5-ene and an amine. The amine generated bythe reaction of the disubstituted carbodiimide and dipropylene triaminedepends on the R/R¹ group. For example, the amine will be isopropylamine if R/R¹ is an isopropyl group, or cyclohexylamine, if R/R¹ is acyclohexyl group. This amine byproduct can be distilled off during thecourse of the reaction, such that all that remains in the reactionvessel with the 1,5,7-triazabicyclo[4.4.0]dec-5-ene upon completion ofthe reaction is the ethereal solvent and/or the alcohol. Alternatively,the amine byproduct can be removed upon completion of the reaction.

Suitable ethereal solvents that may be utilized in the solvent processof the present invention include, but are not limited to, butyl carbitolformal.

Suitable alcohols (i.e. alcoholic solvents) that may be utilized in thesolvent process of the present invention include, but are not limited tomonoalcohols or polyols, such as 2-butoxyethanol (i.e. butylcellosolve), diethylene glycol monobutyl ether (i.e. butyl CARBITOL),hexaethoxylated bisphenol A polyol and combinations thereof. In certainembodiments, 2-butoxyethanol is used.

In general, the solventless process of the present invention begins byintroducing the disubstituted carbodiimide to a reaction vessel. Next,dipropylene triamine is slowly added to reaction vessel, wherein theresultant mixture begins to react and exotherm. The mixture is thenheated to an elevated temperature and held for a sufficient period oftime to react the disubstituted carbodiimide and dipropylene triamine,first forming an intermediate and then forming1,5,7-triazabicyclo[4.4.0]dec-5-ene and an amine. This amine byproductcan be distilled off during the course of the reaction, or removed uponcompletion of the reaction. A diluent, such as hexaethoxylated bisphenolA polyol, may be added to the formed 1,5,7-triazabicyclo[4.4.0]dec-5-enein the reaction vessel.

The term “an elevated temperature”, when used in the context of thepresent processes is the temperature at which the disubstitutedcarbodiimide reacts with the dipropylene triamine to form the1,5,7-triazabicyclo[4.4.0]dec-5-ene and the amine. In certainembodiments, the elevated temperature is 160° C. or greater, 170° C. orgreater, or 180° C. or greater, and can be as high as 220° C., 230° C.,240° C. or even higher. Typically, a higher temperature results inshorter reaction time. In certain solvent processes, the elevatedtemperature corresponds to the reflux temperature of the etherealsolvent and/or the alcohol or blend that is used. For example, when2-butoxyethanol is used, the elevated temperature corresponds to thereflux temperature of 2-butoxyethanol (about 170° C.). In a particularembodiment, the disubstituted carbodiimide comprises diaryl carbodiimideand the elevated temperature is 160° C. or greater, 170° C. or greateror 180° C. or greater.

The term “a sufficient period of time”, when used in the context of thepresent process, is the time needed to cause the disubstitutedcarbodiimide to substantially or completely react with dipropylenetriamine. By “substantially react” is meant 70% conversion or greater;by “completely react” is meant 85% conversion or greater. This timeperiod may vary, depending upon the exact reaction conditions and, inthe case of the solvent process, depending upon the ethereal solventand/or the alcohol used. Typically, the sufficient period of time willbe 1 to 6 hours, such as 1 to 4 hours or 2 to 4 hours. The degree ofreaction can be determined by analyzing the contents of the reactionvessel using known spectroscopic techniques (IR, ¹³C NMR, etc.) toconfirm the presence or absence of the disubstituted carbodiimide anddipropylene triamine and to confirm the presence of1,5,7-triazabicyclo[4.4.0]dec-5-ene.

In certain embodiments, the processes described herein are performedwithout catalyst.

In certain embodiments, the 1,5,7-triazabicyclo[4.4.0]dec-5-ene isisolated from the ethereal solvent and/or the alcohol throughdistillation at atmospheric pressure. In certain embodiments, after thedistillation process, the 1,5,7-triazabicyclo[4.4.0]dec-5-ene may berecovered in powder form. Alternatively, the1,5,7-triazabicyclo[4.4.0]dec-5-ene may be maintained in solution withthe ethereal solvent and/or with the alcohol for subsequent use. Asnoted above, in both the solvent and solventless processes the aminebyproduct can be removed from the reaction vessel via distillation. Incertain embodiments, this distillation is performed concurrent with thereaction. By “concurrent” is meant the distillation is performed duringthe reaction in which the 1,5,7-triazabicyclo[4.4.0]dec-5-ene is formed.Although the inventors do not wish to be bound by any mechanism, incertain embodiments, distilling off the amine byproduct concurrentlywith the reaction may result in the reaction occurring more efficiently,that is, more quickly and/or with a higher percent conversion.

The isolated bicyclic guanidine (1,5,7-triazabicyclo[4.4.0]dec-5-ene(TBD)), formed in either the solvent or solventless processes describedabove, which is in solution form or powder form, can then be added toany composition in which bicyclic guanidine can be used. For example, incertain embodiments, the bicyclic guanidine formed from the processdescribed herein can be added to an electrodepositable coatingcomposition, such as the electrodepositable coating composition that isdescribed in U.S. Pat. No. 7,842,762, which is incorporated in itsentirety herein by reference.

As used herein, unless otherwise expressly specified, all numbers suchas those expressing values, ranges, amounts or percentages may be readas if prefaced by the word “about”, even if the term does not expresslyappear. Any numerical range recited herein is intended to include allsub-ranges subsumed therein. Plural encompasses singular and vice versa.For example, while the invention has been described in terms of “a”disubstituted carbodiimide, “an” alcohol, “the” R/R¹ group, and thelike, mixtures of these and other components can be used. Also, as usedherein, the term “polymer” is meant to refer to prepolymers, oligomersand both homopolymers and copolymers; the prefix “poly” refers to two ormore. When ranges are given, any endpoints of those ranges and/ornumbers within those ranges can be combined with the scope of thepresent invention. “Including”, “such as”, “for example” and like termsmeans “including/such as/for example but not limited to”.

EXAMPLES

The following examples are intended to exemplify the invention and arenot intended to limit the invention in any way.

Example 1 DIC Route in 2-Butoxyethanol

A 4-neck flask was equipped with a temperature probe, stainless steelmechanical stirrer, and an ice water condenser. Dry nitrogen was sweptthrough the flask, out through the condenser, then through an attachedcold trap containing dry ice and ethanol used to trap isopropylaminedistillate. The flask was charged with 2-butoxyethanol (220 mL) andN,N′-diisopropylcarbodiimide (151.4 g, 1.2 mol), and warmed to 60° C.Then, dipropylene triamine (131.2 g, 1.0 mol) was added slowly. Uponaddition of dipropylene triamine, an exotherm of 40° C. was observed(˜60° C.→100° C.). The reaction was warmed slowly to 170° C. andrefluxed at that temperature for 12 hours. The orange, homogenoussolution was then cooled, poured out of the reaction vessel, and usedwithout further purification. The concentration of TBD in the finalsolution was determined by HPLC (38.8 wt %, 94.6% conversion). ¹³C NMRanalysis indicated that the material consisted solely of1,5,7-triazabicyclo[4.4.0]dec-5-ene in 2-butoxyethanol. ¹³C NMR analysisof the distillate confirmed the capture of the byproduct isopropylamine(129 mL) as the sole compound.

Example 2 DCC Route in 2-Butoxyethanol

A 4-neck flask was equipped with a temperature probe, stainless steelmechanical stirrer, and an ice water condenser. Dry nitrogen was sweptthrough the flask and out through the condenser. The flask was chargedwith 2-butoxyethanol (220 mL) and N,N′-dicyclohexylcarbodiimide (247.6g, 1.2 mol), and warmed to 60° C. Then, dipropylene triamine (131.2 g,1.0 mol) was added slowly. Upon addition of dipropylene triamine, anexotherm of 14° C. was observed (˜58° C.→72° C.). The reaction waswarmed slowly to 170° C. and refluxed at that temperature for 18 hours.The orange, homogenous solution was then cooled, poured out of thereaction vessel, and used without further purification. Theconcentration of TBD in the final solution was determined by HPLC (32.9wt %, 80.2% conversion). ¹³C NMR analysis indicated that the materialconsisted of 1,5,7-triazabicyclo[4.4.0]dec-5-ene and cyclohexylamine(2.5%) in 2-butoxyethanol.

Example 3 DCC Route in Diethylene Glycol Monobutyl Ether

A 4-neck flask was equipped for total distillation, along with atemperature probe and stainless steel mechanical stirrer. Dry nitrogenwas swept through the flask and out through the distillation apparatus.The flask was charged with diethylene glycol monobutyl ether (210 mL)and N,N′-dicyclohexylcarbodiimide (247.6 g, 1.2 mol), and warmed to 60°C. Then, dipropylene triamine (131.2 g, 1.0 mol) was added slowly. Uponaddition of dipropylene triamine, an exotherm of 41° C. was observed(˜61° C.→102° C.). The reaction was warmed to 140° C. and held for 1hour, then heated to 220° C. and held for 2 hours. The orange,homogenous solution was then cooled, poured out of the reaction vessel,and used without further purification. The concentration of TBD in thefinal solution was determined by HPLC (35.4 wt %, 81.0% conversion). ¹³CNMR analysis indicated that the material consisted solely of1,5,7-triazabicyclo[4.4.0]dec-5-ene in diethylene glycol monobutylether. ¹³C NMR and GC/MS analysis of the distillate confirmed thecapture of cyclohexylamine (199 mL).

Example 4 DpTC Route in 2-Butoxyethanol

A 4-neck flask was equipped with a temperature probe, magnetic stir bar,and an ice water condenser. Dry nitrogen was swept through the flask andout through the condenser. The flask was charged, at ambienttemperature, with 2-butoxyethanol (11 mL), N,N′-di-p-tolylcarbodiimide(13.5 g, 0.06 mmol), and dipropylene triamine (6.64 g, 0.05 mol). Anexotherm of 34° C. was observed (˜23° C.→57° C.). The reaction waswarmed slowly to 170° C. and refluxed at that temperature for 15 hours.The orange-brown, homogenous solution was then cooled, poured out of thereaction vessel, and used without further purification. Theconcentration of TBD in the final solution was determined by HPLC (19.9wt %, 79.1% conversion). ¹³C NMR and GC analyses indicated that thematerial consisted of 1,5,7-triazabicyclo[4.4.0]dec-5-ene andp-toluidine (36.8%) in 2-butoxyethanol.

Example 5 DCC Route (100% Solids, Polyol Post-Add, 20% DCC Excess)

A 4-neck flask was equipped for total distillation, along with atemperature probe and stainless steel mechanical stirrer. Dry nitrogenwas swept through the flask and out through the distillation apparatus.The flask was charged with N,N′-dicyclohexylcarbodiimide (247.6 g, 1.2mol) followed by the slow addition of dipropylene triamine (131.2 g, 1.0mol). Upon addition of dipropylene triamine, an exotherm of 31° C. wasobserved (˜24° C.→55° C.). The reaction was warmed to 170° C. and heldfor 1 hour, then heated to 220° C. and held for 2 hours. After the finalhold, hexaethoxylated bisphenol A polyol (417.0 g, 0.85 mol) was addedas a diluent. The orange, homogenous solution was then stirred, cooled,poured out of the reaction vessel, and used without furtherpurification. The concentration of TBD in the final solution wasdetermined by HPLC (21.3 wt %, 94.4% conversion). ¹³C NMR analysisindicated that the material consisted solely of1,5,7-triazabicyclo[4.4.0]dec-5-ene in hexaethoxylated bisphenol Apolyol. ¹³C NMR and GC/MS analysis of the distillate confirmed thecapture of cyclohexylamine (175 mL).

Example 6 DCC Route (100% Solids, Polyol Post-add, 2% DCC Excess)

A 4-neck flask was equipped for total distillation, along with atemperature probe and stainless steel mechanical stirrer. Dry nitrogenwas swept through the flask and out through the distillation apparatus.The flask was charged with N,N′-dicyclohexylcarbodiimide (210.5 g, 1.02mol) followed by the slow addition of dipropylene triamine (131.2 g,1.00 mol). Upon addition of dipropylene triamine, an exotherm of 32° C.was observed (˜23° C.→55° C.). The reaction was warmed to 170° C. andheld for 1 hour, then heated to 220° C. and held for 2 hours. After thefinal hold, hexaethoxylated bisphenol A polyol (319.8 g, 0.65 mol) wasadded as a diluent. The orange, homogenous solution was then stirred,cooled, poured out of the reaction vessel, and used without furtherpurification. The concentration of TBD in the final solution wasdetermined by HPLC (28.0 wt %, 93.7% conversion). ¹³C NMR analysisindicated that the material consisted solely of1,5,7-triazabicyclo[4.4.0]dec-5-ene in hexaethoxylated bisphenol Apolyol. ¹³C NMR and GC/MS analysis of the distillate confirmed thecapture of cyclohexylamine (229 mL).

Whereas particular embodiments of this invention have been describedabove for purposes of illustration, it will be evident to those skilledin the art that numerous variations of the details of the presentinvention may be made without departing from the invention as defined inthe appended claims.

What is claimed is:
 1. A method for producing1,5,7-triazabicyclo[4.4.0]dec-5-ene comprising: (a) forming a mixturecomprising a disubstituted carbodiimide, dipropylene triamine and anethereal solvent and/or alcohol; (b) heating said mixture at atemperature of 160° C. or greater to cause said disubstitutedcarbodiimide to react with said dipropylene triamine; and c) distillingoff by product from the reaction step of b), wherein step c) and step b)are concurrent.
 2. The method of claim 1, wherein said heating is at atemperature of 170° C. or greater.
 3. The method of claim 1, whereinsaid disubstituted carbodiimide comprises dialkylcarbodiimide.
 4. Themethod of claim 3, wherein said dialkylcarbodiimide comprisesN,N′-diisopropylcarbodiimide, N,N′-dicyclohexylcarbodiimide, orcombinations thereof.
 5. The method of claim 1, wherein saiddisubstituted carbodiimide comprises diarylcarbodiimide.
 6. The methodof claim 5, wherein said diarylcarbodiimide comprisesdi-p-tolylcarbodiimide.
 7. The method of claim 1, wherein the mixture ofstep (a) is formed in alcohol.
 8. The method of claim 7, wherein saidalcohol comprises 2-butoxyethanol, diethylene glycol monobutyl ether,hexaethoxylated bisphenol A polyol, or combinations thereof.
 9. A methodfor producing 1,5,7-triazabicyclo[4.4.0]dec-5-ene comprising: (a)forming a mixture comprising disubstituted carbodiimide and dipropylenetriamine; (b) heating said mixture to cause said disubstitutedcarbodiimide to react with said dipropylene triamine; and (c) distillingoff byproduct from the reaction step of (b), wherein step (c) and step(b) are concurrent wherein said method is performed in the absence of anethereal solvent and/or alcohol.
 10. The method of claim 9 furthercomprising (d) adding a diluent after step (c).
 11. The method of claim9, wherein said disubstituted carbodiimide comprisesdialkylcarbodiimide.
 12. The method of claim 9, wherein saiddisubstituted carbodiimide comprises diarylcarbodiimide.